1. Field of the Invention
The present invention relates to a medical implantable lead having a proximal end and a distal end, and a flat elongate body.
2. Description of the Prior Art
A medical implantable lead is preferably designed as thin as possible. It also needs to be well flexible in order to be able to follow narrow winding body cavities. A conventional structure is an elongate lumen defined, i.e. formed, by coiled conductors carrying electrical signals for different applications. The lumen is used for facilitating implantation of the flexible lead into a body by means of a slightly stiffer guide wire, stylet or the like, which is inserted into the lumen and manoeuvred by an operator, typically a surgeon.
Modern technology imposes demands on increased ability to carry more and more signals for sensing, monitoring and commanding purposes. These demands introduce a conflict between outer diameter of the lead and number of available conductors within the lead, since with the traditional design of the lead a coaxial addition of a conductor coil adds significantly to the diameter of the lead.
Therefore different ways to increase the number of conductors without increasing the outer dimensions of the lead have been proposed. For example, in U.S. Pat. No. 5,201,903 there is shown a multiconductor electrical cable, which is stated to be suitable for implantation in living bodies. The main embodiment has several, e.g. seven, separately insulated conductors, helically twinned to a cable, which is provided with a further insulating coating forming a single, or integral, unit. The conductors are thin wire conductors having diameters as small as about ten micrometers. There is no teaching in this patent as to how to implant such a cable into the body. A central lumen is disclosed, which is meant to be used as a catheter, but being to thin to work as a lumen for a stylet or the like. However, it would probably be a simple task to enlarge the central lumen. Notwithstanding the positive properties of such a thin multi conductor cable, it is also has disadvantages. The manufacturing process of handling such thin wire conductors and embedding them in an insulating material to form the electrical cable is rather a difficult task.